OSPF on-demand configuration was designed for efficient operation over on-demand circuits like ISDN, X.25 switched virtual circuits (SVCs), and dialup lines. Since these are billed on usage basis, you don’t want your OSPF protocol to keep these circuits up 24-7. This feature allows OSPF to suppress periodic hellos and the periodic refreshes of LSAs are not flooded over the demand circuit.
These packets bring up the link only when they are exchanged for the first time, or when a change occurs in the information they contain. This feature is useful when you want to connect telecommuters or branch offices to an OSPF backbone at a central site. In this case, OSPF for on-demand circuits allows the benefits of OSPF over the entire domain, without excess connection costs. Periodic refreshes of hello updates, LSA updates, and other protocol overhead are prevented from enabling the on-demand circuit when there is no “real” data to send.
Configuring this is pretty basic, as long as you have OSPF enabled on your router, you can use the interface configuration command to enable this feature. If this is being enabled on a point-to-point circuit, then you only need this command on one end of the circuit.
Router(config-if)#Â ip ospf demand-circuit
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